Download Station 11

Reporting Category 3
Biological Evolution
and Classification
Station 11
Natural Selection and Adaptation
Essential Question – Bell Ringer
• How can natural selection affect the
frequency of the occurrence of certain
traits in a population over many
generations?
Through the process of natural selection, certain traits of
organisms that are able to adapt to changing conditions in an
ecosystem or biome become more prevalent and are more
likely to be passed on to the organisms’ offspring. Traits that
are not beneficial to an organism are less likely to be passed on
to successive generations, and organisms that are not as fit are
less likely to pass on their traits to successive generations.
Pre-Preview Question
During his visit to the Galapagos Islands, Charles Darwin
discovered 14 distinct species of finches. These groups had been
geographically isolated from one another. Many of them lived on
different islands. The species of finches differed mainly in feeding
behavior, beak structure, and body size. Yet, all of the species
shared some characteristics.
• Which of the following statements best explains differences
between the finches?
A. The beaks of the finches changed so the finches could better
access different sources of food.
B. The beaks of the finches changed so all of the finches could eat
the same types of food.
C. The beaks of the finches changed as the species of finches
migrated to the same island.
D. The beaks of the finches changed as the finches' body sizes
changed.
Pre-Review Question
• The forelimbs of a frog and a horse are
examples of structures that are
A. Heterotrophic
B. Homozygous
C. Hermaphroditic
D. Homologous
Pre-Review Question
• In an area of Indonesia where the ocean floor is littered with empty
coconut shells, a species of octopus has been filmed "walking" on
two of its eight tentacles. The remaining six tentacles are wrapped
around its body. Scientists suspect that, with its tentacles arranged
this way, the octopus resembles a rolling coconut. Local predators,
including sharks, seem not to notice the octopus as often when it
behaves in this manner. This unique method of locomotion has been
utilized by successive generations of octopi through —
A. Selective breeding of the octopus species
B. Competition between octopi and their predators
C. The process of natural selection
D. Ecological succession in marine habitats
Use this information to answer
the question on the next slide.
Using the chart on the
previous slide, write and
answer this question in your
journal.
• Which cottontail rabbit—A, B, or C—in the
table above is considered the most fit of
the three rabbits? Support you answer
with data from the table.
Copy this
chart into
your
journal and
fill in the
example
information
using the
pictures on
the next
slide.
The Springbok antelope and the Pronghorn antelope are
examples of convergent evolution. The seal’s flipper and the
bird’s wing are examples of divergent evolution. The Yucca
plant and the Yucca moth are examples of coevolution.
Discuss with your partner….
Read and discuss the definitions of biological influences
and physical influences in the glossary. Explain the role
that biological and physical influences play in natural
selection and the effect these influences can have on an
ecosystem’s populations and species.
Biological influences such as diseases may cause weaker
organisms to die out and prevent the passage of their traits
to other generations of organisms. Physical influences such
as a tsunami may remove food sources for organisms or
destroy entire ecosystems. Different organisms may
repopulate the emerging, ecosystem changing the direction
of evolution or type of evolution from the previous
one.
Discuss with your partner….
What is the difference between the cactus on the left and the
cactus on the right?
The cactus on the left is covered with spines or needles;
the one on the right does not have them.
Discuss with your partner….
What effect does the deer’s feeding behavior have on the
ability of each type of cactus to survive and reproduce?
The deer feeds only on the spineless cactus. Over time, if the
deer reproduces successfully, the spineless cactus will no
longer be part of the desert biome, leaving only the cactus
with spines to reproduce. If the deer cannot find another food
source or does not have traits that enable it to adapt, it must
leave the biome or possibly become extinct.
Discuss with your partner….
How does the deer’s feeding behavior with respect to the
cacti in this desert biome illustrate natural selection or the
survival of the fittest?
In order for natural selection to occur, it must meet three conditions:
variations in characteristics, differences in fitness, and heritable traits The
two cacti met these conditions: They had variations in their
characteristics—one with spines, one without. They had variations in their
abilities to survive and reproduce—the deer ate both the spineless cactus
pad and its flowers, meaning it couldn’t reproduce. The trait of
spinelessness therefore cannot be passed down to successive
generations and is therefore no longer heritable.
I need to remember……..
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No organism or population of organisms is perfectly adapted to its
ecosystem.
Natural selection does not produce perfection in the organisms that are
adapted to an ecosystem.
Adaptations are due to genes that are heritable.
Natural selection occurs as the result of three conditions: variations in
characteristics in a population, heritable traits, and differences in fitness
among organisms within a species.
Survival of the fittest does not refer to how physically fit or strong an
organism is; rather, it refers to an organism’s ability to reproduce and pass
on its traits to the next generation.
Natural selection does not act on an individual to make it better adapted to
its environment.
There are biological and physical influences that determine the survival and
success of organisms.
There are three types of evolution that occur as a result of natural
selection— divergent evolution, convergent evolution, and coevolution.
Post Review Question
• A population of mosquitos is sprayed with a new
insecticide. Most of the mosquitos are killed but a few
survive. In the next generation, the spraying continues,
but still more are immune to the insecticide. How could
these results be explained according to the present
concept of evolution?
• A. The insecticide caused a mutation in the mosquitos.
• B. The mosquitos learned to fight the insecticide.
• C. A few mosquitos in the first population were resistant
and transmitted this resistance to their offspring.
• D. The insecticide caused the mosquitos to develop an
immune response which was inherited.
Post Review Question
• According to the theory of natural selection, why are
some individuals more likely than others to survive and
reproduce?
A. Some individuals are better adapted to their
environment than others.
B. Some individuals pass on to their offspring new
characteristics they have acquired during their lifetimes.
C. Some individuals do not pass on to their offspring new
characteristics they have acquired during their lifetimes.
D. Some individuals tend to produce fewer offspring than
others in the same environment.